Hydraulic Fracturing Process for Deviated Wellbores

ABSTRACT

A method of stimulating an interval in a hydrocarbon reservoir equipped with a deviated wellbore having a casing, wherein said interval comprises at least two sequential stages in said wellbore without isolation means, said method comprising:
     i) introducing a first stage   ii) introducing a second stage in the same wellbore   wherein said first stage, and second stage are not separated by any isolation means; and optionally   iii) recovering hydrocarbon from said hydrocarbon reservoir to a surface.

FIELD OF THE INVENTION

This invention is directed to a method of fracturing a plurality ofstages, without the need of any isolation or diversion means, in asubterranean formation from a deviated wellbore penetrating ahydrocarbon containing formation.

BACKGROUND OF THE INVENTION

In the production of hydrocarbons from subterranean rock formationspenetrated by wellbores, a commonly used technique for stimulating suchproduction is to create and extend fractures in the formations. Mostoften, the fractures are created by applying hydraulic pressure to thesubterranean formations from the wellbores penetrating them. That is, afracturing fluid or a combination of fluids are pumped through thewellbore and into a formation to be fractured at a rate and pressuresuch that the resultant hydraulic pressure exerted on the formationcauses one or more fractures to be created therein and/or extends anyexisting fractures (natural or otherwise) in the formation. Thefractures are extended by continued pumping, and optionally, thefractures are: i) either propped open by a propping agent (a proppant),e.g., sand, deposited therein or ii) the fracture faces are etched by areactive fluid such as an acid whereby hydrocarbons contained in theformation readily flow through the fractures into the wellbore.

Several fracturing techniques are known for use in stimulation ofhydrocarbon recovery. Examples of several prior art techniques areprovided in the following patents:

U.S. Pat. No. 4,415,035 (“the '035 patent”) teaches, for example, amethod for forming fractures in a plurality of hydrocarbon-bearingformations communicating with a vertical well penetrating a subterraneanearth formation during a single fracturing treatment without having toresort to separate and individual fracturing through use of mechanicalpackers, limited entry, ball sealers, diverting agents or other pluggingmeans as taught in the prior art (column 2 lines 26-34). The '035 patentalso teaches that the perforations of all stages are to be completedprior to introduction of the fracturing fluid in the vertical wellbore.This is known in the art as “Hail Mary” fracturing. The '035 patentpertains solely to vertical wellbores without any teaching of fracturingin horizontal or deviated wellbores. It is known and agreed that thegeometry of the well plays a significant role in fracture creation andpropagation.

Love, T. G. et al., “Selectively Placing Many Fractures in OpenholeHorizontal Wells Improves Production” SPE International Conference onHorizontal Well Technology, 1-4 Nov. 1998, Calgary, Alberta, Canadateaches a method of fracturing a wellbore by hydrajet technology. Thetechnology comprises fracturing the entire wellbore using acid. A sandpill is inserted in the wellbore after each fracture prior to fracturingthe next location. Although the article alleges that the fracturingprocess does not require any plugs, it does require sand pills (i.e.diverter or isolation means) in order to establish and maintain workingpressure. Further this reference requires perforation of all the areasof interest in the wellbore prior to the fracturing process.

U.S. Pat. No. 4,850,431 (“the 431 patent”) teaches a method of forming aplurality of spaced, substantially parallel fractures from a deviated orhorizontal wellbore. In this method, a casing is placed in the deviatedwellbore, and a plurality of spaced fracture initiation points arecreated therein by forming a set of perforations of predetermined numberand size through the casing and into the formation. Hydraulic pressureis applied under predetermined conditions to the perforations at thefracture initiation points simultaneously to extend a plurality ofspaced substantially parallel fractures in the formation from thedeviated wellbore (i.e. simultaneous multi-stage fracturing).

After the sets of perforations at the fracture initiation points arecreated throughout the entire wellbore, each set of perforations at eachfracture point is isolated, and hydraulic pressure is applied thereto(column 2 lines 41-46). At the paragraph bridging columns 5 and 6, the431 patent states this is the most preferred technique. The only examplein the 431 patent specifically states at column 7 lines 29-32 “Prior topumping the fracturing fluid containing propping agent into thewellbore, each of the sets of perforations at the fracture initiationpoints is isolated . . . .”

U.S. Pat. No. 4,977,961 (“the 961 patent”) teaches a method of creatingparallel vertical fractures in horizontal or inclined wellbores. The 961patent teaches two ways of fracturing a horizontal well with regard tosecond perforations following the first perforations.

The 961 patent teaches the following steps:

-   -   a) Perforating a casing at a first perforation point;    -   b) Perforating a casing at a second perforation point;    -   c) Applying hydraulic pressure at first and second perforations        simultaneously; and    -   d) Producing the formation fluids to the surface.

An alternative process comprises the following steps:

-   -   a) Perforating the casing at the first perforation point with a        first pair of perforations;    -   b) Applying hydraulic pressure to propagate a fracture;    -   c) Isolating the first pair of perforations from fluid        communication;    -   d) Perforating the casing at the second perforation point with a        second pair of perforations; and    -   e) Applying hydraulic pressure to initiate and propagate the        fracturing at the second pair.

PCT Application WO 2012/054139 (“the 139 patent”) teaches a method ofcreating a network of fractures in a reservoir. This method includescreation of fractures by injecting fracturing fluid, monitoring of thestress and then expanding the fractures by continuous injection offracturing fluids in the wellbore. The 139 patent also requires the useof isolation or diversion means such as packers, fracturing ports,mechanical plugs, sand plugs, sliding sleeves, and other devices knownin the art.

The cost of stimulating production from horizontal wellbores oftenrequires hydraulic fracture stimulation for the well to be commercial.The cost of hydraulic fracture equipment and wellbore interventionequipment required for these operations are often based on the amount oftime the equipment is on location regardless of whether the equipment isin use. If the amount of this “stand-by” time on location can bereduced, the cost of the hydraulic fracture stimulation operation can bereduced, and in many cases significantly. A typical hydraulic fracturestage might take 3 to 8 hours or more to complete. The operationsperformed during this time are often wellbore preparation such assetting plugs and perforating the pipe while the fracturing equipment isshut down and nonproductive. Equipment providers may charge standbycharges for this down time, or they may charge a day rate or a flat ratefor the equipment per day regardless of whether the equipment is inoperation. If the amount of time required to set plugs and perforate thewellbore were eliminated and/or taken off the production path, that is,these operations were performed while the hydraulic fracturing stageswere being pumped, the operator would finish the fracturing projectsooner and one benefit would be a reduction in overall cost associatedwith the process.

There is a process referred to above know in the industry as Just InTime Perforating, (JITP). It is our understanding that the processrequires a mechanical isolation method to divert the fracturing fluidsfrom one perforated interval to the next. These perforations are createdwith shaped explosive charges or high velocity fluids, such as Hydra-Jetor Abrasive-Jet processes. It is our understanding that the initialinterval is perforated by means understood in the industry. After afluid path is established from the casing into the subterranean stratavia these holes (perforations) in the casing, hydraulic fracturingbegins by pumping fluid or gas into the casing at sufficient pressure togain entry into the zone of interest to stimulate production of thefluid or gas i.e. hydrocarbons contained therein. The next step is thefirst part of the existing JITP process. The perforating device, (e.g.:a “Select Fire” wireline perforating (“perf”) gun), is pulled up thewellbore to the next zone of interest in preparation for perforatingoperations, while pumping of the previous interval continues.

In traditional applications of multistage hydraulic fracturing, the nextstep would have been to pull the perforating device completely out ofthe wellbore, with the exception of some coil tubing operations whereperforating takes place with high velocity abrasive fluid pumped downthe coil tubing at sufficient rates to create holes in the casing. Inthis exception, the fracturing fluid may be pumped down the annular pathonly, down the tubing or via a common manifold, that is, both tubing andannular space. The JITP process utilizes the Annular Path Method (seefor example “Packerless Multistage Fracture-Stimulation method Using CTPerforation and Annular Path Pumping”, L. East, J. Rosato, M. Farabee,and B. W. McDaniel, SPE Annual Technical Conference and Exhibition, 9-12Oct. 2005, Dallas, Tex.) to continue the fracturing process while thewireline remains in the wellbore. The annular path in this case is theannular space between the wireline and the internal diameter of thehole, e.g.: production casing. This method includes stimulation via theannular path method that utilizes a mechanical isolation/diversionmethod, e.g.: perforation ball sealers (“Perf Balls”). Perforation ballsealers are stiff balls of sufficient strength that will seal aperforation from flow in the direction of the wellbore into the zone ofinterest during high pressure stimulation operations understood by thoseknowledgeable in hydraulic fracturing and/or acidization.

When sufficient fracturing fluid has been pumped into the zone ofinterest per the pumping schedule or at such point where the end oftreatment is determined, preferably by independent means by thosesupervising the treatment, preparations are made to perforate thesubsequent zone of interest via select fire perforating. “Select fire”is a term understood by those skilled in the oil and gas extractionindustry as a perforating device (“perf gun”) capable of multipleoperations with expendable perforation charges. Multiple perf guns aredeployed on a wireline to permit multiple perforation operations viatechnology know to the person skilled in the wireline perforationindustry. Each perf gun is either selected to fire on demand viamultiple conductor wires deployed in the wireline from the surface tothe perf gun, or selected to fire on demand via Internet Protocoldevices built into both ends of the wireline, one a sender at thesurface and one a receiver at the perf gun. Other methods in the commondomain to form multiple interval perforations along sections of awellbore casing may also be implemented.

Since the perf gun is pulled along the wellbore to the next zone ofinterest during the first step, the perf gun when fired will perforatethe next zone of interest just in time for fluid or gas to enter theperforations. The perf gun however is not fired until the previousinterval has been mechanically sealed off from further injection offracturing fluid or gas. The sealing method deployed is understood to bethe use of perforation ball sealers of sufficient size to seal off theexisting perforations, but small enough to be carried down the casingwith the stimulation fluid past the wireline and perf gun tools. Oncethese perforation balls seal existing perforations and begin shuttingoff flow of fracturing fluid to the previous zone of interest, thepressure in the casing rises due to what is referred to as perforationfriction. To those knowledgeable in limited entry theory, perforationfriction increases with increased flow into perforations. The sealing ofthe perforation by the perf balls forces excess fluid into the remainingunsealed perforations. This is seen at the surface as an increase insurface treating pressure. At this instance, the operators are warned itis time to fire their perf guns as the pressure increases to apredetermined pressure within the working limits of the productioncasing in the wellbore. Once this pressure is reach, the perf guns arefired resulting in new perforations in the casing proximate the nextzone of interest, and if sufficient perf balls are deployed, allperforations in the previous zone are now plugged. The fracturing fluidor gas enters the new interval without a change in rate required at thesurface.

As discussed above, the prior art requires the use of isolation ordiversion means to isolate one stage from another, prior to fracturing.The use of isolation or diversion means at each stage is costly, bothfinancially and temporally. The cost associated with deploying, settingand removing plugs in a typical wellbore setup can run up to $1MIL/wellbore. It is known that the removal of a plug is more expensivethan the setting of the plug. Generally the plugs have to be drilled outor otherwise extracted from the bore prior to commencing hydrocarbonrecovery. The time involved in drilling out the plugs is also costly.Furthermore, the use of diesel fuel or other hydrocarbon energy sourcesused to drive pumps and machinery during drilling operations to removethe plugs and the associated waste may have a negative impact on theenvironment.

Some of the costs associated with the prior art processes include (butare not limited to): cost of setting a bridge plug; cost of the bridgeplug; cost of drilling out bridge plugs; cost of surface equipment; costof fluids pumped plus expendables such as bits motors etc.; and the timevalue of money for delayed hydrocarbon production.

Therefore there is a need for a process of generating a plurality offracture points in the hydrocarbon formation with greater efficiency,and optionally lower cost, and further optionally with less deleteriousimpact on the environment. The current invention presents an improvedmethod of forming a plurality of fractures from a single deviatedwellbore.

The process presented in the current invention is an improvement of theabove described processes. This process in one embodiment, saves theoperator the down time normally required to do the following steps:

-   -   a) pulling the wireline deployed perf gun to the surface;    -   b) treating the wellbore for isolating the previous perforation        stage; and    -   c) redeploying of the perf gun after treatment is completed.

SUMMARY OF THE INVENTION

The following terms are used herein to better understand the presentinvention:

Interval—a plurality of stages without any isolation or diverter meanstherein.

Stage—a discrete event comprised of a sequence of activities with abeginning and an ending.

Generally a stage comprises a perforation of the wellbore casing andfracturing proximate said perforation.

Isolation means—a device used in isolating one or more stages fromanother stage in order to isolate, restrict or direct the acceptance offracturing fluids at the appropriate time at a predetermined interval.

Examples of isolation means include but are not limited to:

Bridge Plugs—solid in cross section with sealing elements that makecontact with the wellbore casing internal diameter (ID) providing ahydraulic seal where fluids are not able to transmit from one side ofthe plug to the other per design.

Fracking Plugs or Frac Plugs—solid mandrels that have a conduit throughthe center to permit flow in one direction or both. Ultimately, flow isonly permitted in one direction during stimulation operations. Fracplugs do not permit flow from the surface through the device, but willpermit flow from below the device in a direction toward the surface, inthe case of a wellbore with one surface access point. The variousmechanisms employed are known to those well versed in the art oilfieldtools and caring attachments to be, darts check valves, ball and seats,ball valves, caged balls that are provided by various oilfield servicecompanies.

Sand Plugs (Sand Pills)—early references to placing sand in verticalwell casings called this the “Pine Island” technique. Sand is placed byvarious means to form a restriction to flow above existing access pointsin the direction below the next or subsequent stage. In the Pine Islandtechnique, sand was mixed with water and dumped into the well casingsuch that it would fall into the bottom of the well, covering existingcasing access points, in this case perforations in pipe. In the case ofhorizontal wellbores, the sand plug is place by mixing and pumping sandvia tubular conduits established with their bottom ends near existingcasing access points. Well fluid is permitted to circulate betweenconduits either up the tubing well casing annulus, or up the tubing whenpumping on the well tubing casing annulus. Once in place, the sand plugprovides sufficient resistance to fluid flow such that the underlyingcasing access points are isolated from receiving additional stimulationfluid.

Solid Plugging Material

Perforation ball sealers—rigid spherical devices designed to followstimulation fluids to openings in the well casing where they effectivelylodge restricting flow of additional fluid. The openings are renderedisolated from the bulk of the fluid introduced into the well casing fromthat point, until released from said opening or it loses its solid formas in the case of Santrol product marketed as “BioBalls”™. Early deviceswere described as RCN Perfpac balls, RCN being Rubber Coated Nylon.

Rock Salt—graded water soluble salts that will bridge any opening in thewell casing capable of accepting fluid. Once in place, the materialrestricts flow of subsequent fluid entering said access point. One ofthe examples is marketed as TBA-110 or under various other trade names.Another example is Benzoic Acid Flakes or any other solid material thatis soluble in water or oil, or loses its solid form by any means intime. This material isolates any opening capable of accepting fluid aswith all others in this category. This may be marketed as TLC-80.

Any material or device introduced into a well casing in a positiondirectly opposite or above existing access points in said well casingwith the intention to divert fluid past said access points, or to stopfluid from entering said well casing access points. Examples mayinclude: packers, slick line plugs, sliding sleeves and more.

Well casing—Any device or method that serves as a conduit and a liningor barrier of petroleum wellbore, preventing said wellbore fromcollapse, protecting the ground water from contamination and safelyconducting drilling and subterranean fluids to the surface. For example,but not limiting, steel pipe cemented in place.

Fracturing or Fracking Fluid—Water and water containing various chemicaland mineral additives known to those well versed in the art and scienceof general oil and gas well stimulation as fracking fluid. Said frackingfluid, also referred to as fracturing fluid or stimulation fluid, mayinclude various industrial gases such as, carbon dioxide, nitrogen, orvarious compositions of natural gas such as methane, ethane, propane orbutane, or hydrocarbon liquids such as lease crude, or diesel.

“Plug and Perf”—one of many methods for fracturing a hydrocarbonreservoir. The wellbore for a plug and perf job is generally composed ofstandard joints of steel casing, either cemented or uncemented, which isset in place at the conclusion of the drilling process. Once thedrilling rig has been removed, a wireline truck is used to perforatenear the end of the well, following which a fracturing job is pumped(commonly called a stage). Once the stage is finished, the wirelinetruck will set a plug in the well to temporarily seal off that section,and then perforate the next section of the wellbore. Another stage isthen pumped, and the process is repeated as necessary along the entirelength of the horizontal part of the wellbore.

Access (access point)—this is a point of communication between thewellbore and the formation. The access point can be created by any meansknown in the art. For example, but not limiting, it can be made by aperforation using a perforating gun (“perf gun”), or other means. Theaccess point can have at least one passage through the casing of thewellbore, or have a plurality of passages through the casing alsoreferred to as a cluster. The plurality of perforations may be in oneline along the length of the casing, opposite each other along thediameter of the casing, and/or positioned in a specific directioncorresponding to a point of interest in the formation, or may berandomly positioned throughout the casing.

Formation—a subterranean zone, such as rock or shale development,comprising a hydrocarbon deposit.

The process of the current invention reduces and/or eliminates the useof an isolation plug (or diverter means) and although not being limitedto this mechanism, it is believed relies on pressure differences/rockstress changes to naturally divert the fracturing fluid into the newperforations.

The process of the current invention, in one embodiment stimulates a newfracture in the new perforations by the introduction of fracturing fluidin the new perforations, therefore stimulating new rock/shale (resultingin new fractures), rather than have the fracturing fluid go into theprevious fracture without stimulating new rock/shale through the newperforations. This is accomplished without the need for isolation ordiverter means, as is needed in the prior art.

According to one aspect of the invention, there is provided a method ofstimulating a new interval, in the recovery of hydrocarbons, in anunderground hydrocarbon reservoir, from a deviated wellbore. The methodcomprises the introduction of at least two sequential stages into saidwellbore without isolation means. Said method comprises the followingsteps:

i) introducing a first stage by:

-   -   a) creating a first access point through a wellbore casing into        a hydrocarbon formation;    -   b) introducing at least one fracturing fluid to said first one        access point, at a predetermined rate and pressure to create at        least one fracture in the formation, proximate said access point        to stimulate hydrocarbon production from said hydrocarbon        formation;        ii) introducing a second stage in the same wellbore by:    -   a) creating a second access point, distant said first access        point, through said wellbore casing into said hydrocarbon        formation proximate the first stage;    -   b) introduce at least one fracturing fluid to said second access        at a predetermined rate and pressure to create at least one        fracture in the formation, proximate said access point to        stimulate hydrocarbon production from said hydrocarbon        formation;        iii) recovering said hydrocarbons from said hydrocarbon        reservoir by means known in the art.

According to another aspect of the invention, there is provided a methodof fracturing a plurality of stages, without the need of any isolationor diversion means, in a wellbore, preferably a deviated wellbore,penetrating a subterranean hydrocarbon formation. In one embodiment, themethod comprises:

-   -   i) drilling a substantially vertical wellbore into the formation        and deviating from said substantially vertical wellbore to form        a deviated wellbore from said substantially vertical wellbore at        an angle and direction substantially parallel to the ground;    -   ii) introducing a casing in the deviated wellbore;    -   iii) introducing a first stage by creating an access point        through the casing into the formation;    -   iv) introducing at least one fracturing fluid to said access        point, preferably at a predetermined rate and pressure to create        at least one fracture in the formation, proximate said access        point of said first stage;    -   v) introducing a second stage by creating an access point        through the casing into the formation;    -   vi) introducing at least one fracturing fluid to said access        point, preferably at a predetermined rate and pressure to create        at least one fracture in the formation, proximate said access        point of said second stage; and    -   vii) recovering the hydrocarbon from said formation,        wherein said first stage and second stage are not isolated from        each other.

In a preferred embodiment, the pressure conditions of the wellbore aremonitored to determine the moment of completion of the first stage andthe commencement of forming the second stage.

In yet another preferred embodiment, proppants are introduced with thefracturing fluid, to prop the fractures in the formation.

Preferably, the deviated wellbore extends substantially horizontally orat any operational angle of up to 45° from the heel of an initialsubstantially vertical wellbore. More preferably, the deviated wellboreextends substantially horizontally or at any operational anglesubstantially 90° of vertical, preferably +/−10°, more preferably +/−5°.Alternatively the wellbore may be of variable geometry and itssubstantially horizontal part can vary its direction and elevationangles.

Preferably the access point is comprised of at least one perforation ina direction substantially perpendicular to the wellbore casing. Morepreferably, the access point is comprised of a plurality ofperforations. The perforation or perforations may be positioned alongthe length of said casing, or along the perimeter of said casing. In afurther embodiment, the direction of any of the perforations may varyfrom substantially perpendicular to allow access by the fracturing fluidto the formation in order to cause or propagate a fracture in theformation proximate said perforation(s).

Preferably, the fracturing fluid may comprise at least one liquid, gas,or combination thereof, preferably with at least one solid. Whileseveral types of fracturing fluid compositions may be introducedconsecutively through the access point to the formation, in a preferredembodiment, the fracturing fluid may further comprise proppants, to propthe fracture. Examples of proppants include, but are not limited to,natural sands, manmade ceramics, bauxites etc.

Preferably, the recovery process of hydrocarbons comprises:

-   -   i) terminate the injection of fracturing fluids;    -   ii) reduce the pressure at the wellbore to allow entry of the        hydrocarbons from the fracture in the formation into the        wellbore via the perforations;    -   iii) optionally transfer the hydrocarbons to the surface; and    -   iv) collect the hydrocarbons.

Preferably the recovery process of hydrocarbons is implemented with theuse of recovery equipment which may comprise electrical, mechanical,active or passive equipment. In some instances some or all of thehydrocarbons maybe recovered by the resultant pressure build up in thewellbore from the introduction of the fracturing fluid(s).

According to yet another aspect of the invention, the stimulation of anew interval involves an introduction of at least two stages notseparated by any isolation means. In one instance, the range of stagesmay comprise between three to thirty stages, or more if desired. Thenumber of stages in an interval may depend on the type of formation,length of wellbore, overall thickness of the formation, proximity of thewell and wellbore to other wells and wellbores.

According to yet another aspect of the invention there is provided atleast one interval, in a deviated wellbore, said interval comprising:

a first stage having a perforated and fractured access point, and asecond stage, preferably having a discrete and separate perforated andfractured access point to said first stage access point; wherein saidfirst stage and said second stage are not isolated from each other.Preferably said interval comprises at least three consecutive stages.

According to still another aspect of the invention, there is provided amethod of stimulating a hydrocarbon reservoir comprising stimulating atleast two intervals according to the methods described above, whereinsaid at least two intervals comprise at least two stages, preferably atleast three stages, and wherein said at least two intervals areseparated by isolation means. Prior to hydrocarbon recovery saidisolation means are altered to allow flow from said interval into thewellbore, preferably said isolation means is removed from the wellbore.

According to yet another aspect of the invention there is provided amethod of stimulating a new interval, in a substantially horizontalwellbore, in a hydrocarbon reservoir. Said method comprises introducingtwo or more sequential stages into said wellbore without isolation meansbetween said stages, said method comprising:

i) introducing a first stage by:

-   -   a) creating a first access point through a wellbore casing into        a hydrocarbon formation;    -   b) introducing at least one fracturing fluid to said first        access point, preferably at a predetermined pressure and rate,        to stimulate hydrocarbon production from said hydrocarbon        formation;    -   c) monitoring operating conditions of said wellbore at a        predetermined time throughout said method;        ii) introducing a second stage in the same wellbore by:    -   a) creating a second access point, proximate said first stage,        through a wellbore casing into a hydrocarbon formation;    -   b) introducing at least one fracturing fluid to said second        access point, preferably at a predetermined pressure and rate,        to stimulate hydrocarbon production from said hydrocarbon        formation    -   c) monitoring operating conditions of said wellbore at a        predetermined time throughout said method;        wherein said first stage, and second stage are not separated by        any isolation means.

In another embodiment, the method of stimulating hydrocarbon recoveryfurther comprises introducing a consecutive stage (or stages) in thesame wellbore by:

-   -   a) creating at least one consecutive access point through a        wellbore casing into a hydrocarbon formation proximate a        previous stage;    -   b) introducing at least one fracturing fluid to said consecutive        access point, preferably at a predetermined pressure and rate,        to stimulate hydrocarbon production from said hydrocarbon        formation;    -   c) monitoring operating conditions of the wellbore at a        predetermined time throughout said method;    -   d) terminating stimulation to allow for recovery of        hydrocarbons; and    -   e) recovering hydrocarbons from said hydrocarbon reservoir by        means known in the art;        wherein said first stage, second stage and the consecutive stage        (or stages) are not separated by any isolation means.

The length of each stage will be determined by the overall length of thewellbore, the location of the wellbore and formation characteristics.Preferably the length of each stage may be from about 10 to about 300meters, more preferably from about 100 to about 200 meters.

The interval between stages can range from a predetermined length,preferably from about 10 to about 100 meters, in another instance, theinterval can also be more than 100 meters.

The distance between each access point may be determined by techniquescommon to those knowledgeable in the art. These techniques may include,but are not limited to analytic or numeric models or analog laboratorymodels as deemed necessary to effectively stimulate hydrocarbonproduction. Such models may include, but are not limited to fracturegrowth simulations as well as economic evaluations such as Net PresentValue or Return on Investment calculations based on the cost of goodsand services employed as well as the current or future selling price ofNatural Gas and/or Oil. Preferably, the distance between each accesspoint in each stage may be up to 25 meters. For example, a 1000 meterinterval in a wellbore may have 10 stages of 100 meters/stage, with eachstage comprising as few as one and as many as 10 or more access points.

Preferably, each access point comprises at least one perforation orpoint of access. More preferably each access point comprises a clusteror plurality of perforations proximate each other at a predetermineddistance from each other. Preferably each perforation in the cluster ispositioned at a distance of less than one meter from each other in thesame wellbore.

According to yet another aspect of the invention there is provided amethod of fracturing multiple stages in hydrocarbon deposits fromintervals in a horizontal wellbore, without using isolation means.Examples of isolation means include but are not limited to ball sealers,mechanical packers, or particulate bridging material, or any otherisolation means or mechanical means as discussed herein

Said method comprising the steps of:

-   -   a) selecting a wellbore appropriate for carrying out the method        of fracturing without the use of isolation means;    -   b) selecting an appropriate stage location in said wellbore,        optionally based on seismic and/or other measurements and        studies such as but not limited to geophysics, petrophysics,        petroleum geology, structural geology and reservoir engineering;    -   c) providing at least one perforation, preferably a set of        perforations at a first opening for the first stage of the        wellbore;    -   d) pumping at least one stimulation fluid or sequence of        stimulation fluids into said at least one perforation;    -   e) observing the injection rates and pressure in the stage        selected;    -   f) selecting an appropriate stage location in said wellbore,        optionally based on seismic and/or other measurements and        studies such as but not limited to geophysics, petrophysics,        petroleum geology, structural geology and reservoir engineering,    -   g) providing at least one perforation, preferably a set of        perforations at a consecutive opening for the consecutive stage        of the wellbore without use of isolation means.    -   h) pumping at least one stimulation fluid or sequence of        stimulation fluids into said at least one perforation;    -   i) observing the injection rates and pressure in the stage; and    -   j) optionally repeating steps (f) to (i) without isolation means        between the stages.

The present invention results in effective preparation of thehydrocarbon reservoir for hydrocarbon production by reduction of timespent performing fracturing operations; and/or by reducing thenon-pumping time which is achieved by reducing and/or eliminating therequirement of placing isolation or diverting means such as plugsbetween the stages; and/or by reducing and/or eliminating the need ofremoval of the plugs prior to hydrocarbon production.

Preferably, according to the present invention, the process of hydraulicfracturing, involves fracturing of at least two stages without the needfor a diverting or isolation device. Examples include, but are notlimited to ball sealers, concrete, bridge or sand plug or plugs.

Preferably the fracturing fluid is introduced at a fluid injection ratewith pressure limitations determined by modern wellbore constructionmethods. The expected surface wellhead pressure is dependent on thedepth of the wellbore and the length of the wellbore. The depth of thewellbore affecting expected bottom hole injection pressure and thelength of the wellbore affecting the total fluid friction that must beovercome at a specified injection rate. Typical surface pressure rangesfor a wellbore about 2500 meters below surface, and about 2500 meters inlateral length can range from about more than 15 MPa to about 100 MPa,more preferably from about 35 MPa to about 65 MPa. Furthermore, thepressure may also be dependent on the formation the wellbore issituated. The bottom hole injection pressure required to initiate andextend a hydraulic fracture is dependent on the in-situ rock propertiesincluding regional tectonic stress. These values can be approximated bythose skilled in the process of hydraulic fracture treatment design,utilizing petro physical, sonic, nuclear and electrical wellboremeasurements along with knowledge of petroleum and structural geologyand geophysics. The person of ordinary skill in the art will adjust themethod of introduction, injection rate and fluid composition and volumeas well as the amount and concentration of oilfield propping agents toallow adequate hydrocarbon production stimulation and recovery.

Preferably the fracturing fluid is introduced at a rate ranging fromabout one cubic meter per minute with the lower limit determined by theminimum design rates necessary to effectively create a hydraulicfracture opening within or directly adjacent to a hydrocarbon bearingsubterranean strata by those knowledgeable in the art of the stimulationof horizontal wellbores within hydrocarbon bearing subterranean stratato about 18 cubic meters per minute or more limited on the upperinjection rate only by the available surface pumping equipment deliverypressure and rate limits and the casing safe working pressures, morepreferably from 5 to 15 cubic meters per minute.

According to yet another aspect of the invention, the stimulation orfracturing fluid optionally comprises a tracer or marker, preferably aradioactive material to assist in monitoring operation conditions in thewellbore and determine effectiveness of the fracturing process of thecurrent invention.

Preferably, at least two stages of the horizontal wellbore subsequent tothe first stage are fractured without using conventional divertingtechniques and the location of the subsequent stages are selected byobserving at least one of the injection rates, fluid path and pressurein the stage selected by recording micro-seismic emissions duringstimulation operations via commercial geophysical emission recordingdevices know in the oil and gas industry as geophones deployed either atthe surface in a focused array or deployed into vertical and/orhorizontal wellbores by means known and practices as well as recordingthe presence of gamma emitting tracer element indications in saiddeposit post stimulation operations via the process or processes know inthe industry capable of detecting gamma ray spectrum to ascertain thepresence of said gamma emitting isotopes, preferably scandium, iridiumand antimony.

According to yet another aspect of the invention there is provided acontinuous fracturing process. Once it has been determined by followinga pumping schedule as described above or by decisions based on welltreatment responses, that the current stage should be ceased, theperforation guns would be fired while pumping continues. It has beenobserved that this process results in the newly opened perforationstaking the majority of the incoming fracturing fluid. It has beenobserved via pressure rate responses that if less than 80% of thefracturing fluid enters the new perforations according to the presentinvention, the last stage perforated would be pumped as planned,however, at this stage an isolation means or diverter means will berequired to continue with the process of the present invention. At thisstage, pumping would cease and the wireline perforation gun is pulledout of the wellbore. Preparations would then be made by thoseknowledgeable of horizontal plug and perf operations to perform a plugand perf operation.

Surprisingly, the novel process results in a substantial improvement ofthe fracturing process. In one example, shale gas wells in the HornRiver Basin have been stimulated without the need for mechanicalisolation and led to unexpectedly positive results discussed in moredetail below. Therefore the present invention is also applicable to acontinuous fracturing process.

The invention in one instance is a continuous process for use inhorizontal/deviated multi-stage fracturing operations. The process mayutilize wireline deployed select fire type perforating devices in acontinuous fracturing stimulation process without mechanical divertersor isolation means during the stimulation process. These divertershowever may be deployed following an either planned or unplanned pumpingoperations cessation. It is generally accepted in the industry that theuse of mechanical devices known in the Oil and Gas industry such as,perforation ball sealers, bridge plugs or packers are required toisolate previous frac intervals from current frac intervals whendiversion is necessary, and these devices are planned to be deployedafter the completion of each successive hydraulic fracture stimulationstage. The current invention reduces the frequency of use of these toolsand/or eliminates these mechanical diversion methods in practicalapplication.

In the prior art describing multiple perforations followed by a singlefracturing event, there is only one stage in the interval. In thecurrent invention there are a minimum of two stages (more than onestage) in each interval.

A stage begins after one or more access points are created in a wellcasing to provide direct access to adjacent hydrocarbon bearingsubterranean strata and ends with the creation of subsequent accesspoints in said well casing with hydraulic fracture stimulationactivities performed. To those well versed in Oil and Gas wellstimulation activities, a stage is defined as an activity performed insequence with other physical well activities that are often repeatedwith the intent to achieve a desired well response. In the case ofhorizontal wellbore, hydraulic fracture stimulation operations, thestage is stimulating production from a hydrocarbon bearing reservoirrock at rates that will exceed the natural un-stimulated productionrates.

The number of stages performed in this operation is limited only by thedimensional constraints of the wellbore placed adjacent to thehydrocarbon bearing reservoir. In the current state of the art, a stagesequence is performed over a zone of interest between 25 meters to 150meters more or less, with available horizontal wellbore lengths between1000 meters and 3000 meters in length. For example: a 1000 meterhorizontal wellbore might be stimulated with 10 stages with stagelengths of 100 meters of zone per stage and one access point every 25meters for a total of 4 access points per stage. Another example mightbe to perform the same number of stages in a horizontal wellbore 2000meters in length with 200 meters per stage and one access point every 20meters for a total of 10 access points per stage.

In one embodiment, the process of the present invention may be appliedto at least two stages. That is, following a traditional plug & perfstage, at least two “plugless” stages may be executed. A plug may beplaced up hole subsequent to the plugless stages and the remainingstages may be completed with traditional plug and perf, or with pluglessstages or a combination of plugless and perf & plug stages.

In another embodiment of the invention, the entire well may bestimulated for hydrocarbon recovery entirely with plugless stages.

In another embodiment of the invention, a well may be completed withplugless stages until surface pressure and rate measurements suggestfracturing fluid is entering previous stages, or rather than a hydraulicfracture being created in the stimulation process, the fracturing fluidis entering a fault in the subterranean strata, negating the benefits ofcontinuing the stimulation process as the benefits of stimulating afault are either undetermined, undesirable, or ineffective, at whichpoint the plugless process should be suspended. In this case, a plugwould be run following the last stage and the process would eithercontinue with plugless stages until once more pressure and ratemeasurements suggest the process should again be suspended with theapplication of a traditional plug & perf.

In another embodiment of the invention, perforations may be placed inany position within the wellbore. In one example: the intervaltraditionally referred to as zone three based on sequential stageincrements from the bottom or toe section of the wellbore toward theheel of the lateral section of the wellbore, may be perforated beforethe interval traditionally positioned in the wellbore as zone two, whichwould be in a position closer to the toe than zone three. Zone one istraditionally the first interval closest to the toe or deepest portionof the accessible cased wellbore. Zone two is traditionally the nextinterval in the cased wellbore at a predetermined position in thewellbore, often at equally spaced intervals of fixed length. The zonesare named such from toe to the upper most accessible portion of thecasing sequentially in numeric order, (1, 2, 3, 4 . . . 40). The numberof these zones has increased from just two intervals as performed in theearly development of the Barnett Shale, to as many as 40 or more zones.In the present invention, the zone three interval position when applyingthe plugless fracturing process can now be considered as stage twochronologically, even though it is placed sequentially within thewellbore in the zone three position based on wellbore length. Once thisstage two fracturing treatment is pumped into this zone three position,the stage three interval would be perforated at the zone two position, astep backward in the normal sequence as per the prior art. One benefitof this plugless fracturing process is it gives the operator theopportunity to perform fracturing treatments out of sequence whencompared to traditionally plug and perf methods that require asequential progression from toe of the accessible cased wellbore to theheel section. Typically, operators would not place a mechanical plug inthe wellbore and then drill one out and work backwards as an embodimentof the present invention suggests. Other benefits to this out ofsequence fracturing process takes into consideration the way thesubterranean strata will respond to hydraulic fracture induced stressesand the pattern of fractures that will be developed when placing afracture initiation point between existing hydraulic fractures. Theinventors believe by placing hydraulic fracture initiation points withinexisting hydraulic fractures will take advantage of the altered stressfield within the fractured strata resulting in improved stimulatedreservoir volumes when compared to the traditional sequential fracturingprocess. This process is novel as no hydraulic or mechanical diversionmethod or isolation means are employed permitting the fracturing fluidto enter various positions along the wellbore.

In another embodiment, this process may be applied readily as arefracturing application for existing wellbores. These existingwellbores may have been stimulated with the Plug & Perf method or one ofvarious other multi-stage fracturing methods for cased horizontal wells.That is, cased cemented monobores, cased cemented liner, or caseduncemented wellbores such as those referred to by trade name, PackersPlus STACKFRAC®, Baker FracPoint™, etc., that utilize mechanicalisolation methods deployed on the casing in the form of, mechanicalexternal casing packers, rock packers, and swellable packers. Or in somecases, no mechanical isolation methods are deployed on the externalportion of the casing string. In addition, these methods employ internaldiversion devices (such as ball activated sliding sleeves) to divertfluid to various zones along the casing string. Other multi-stagemethods may have utilized perforation ball sealers as the primarydiversion method, or no diversion at all such as often referred to as a“Hail Mary” frac where the entire wellbore or a portion of the wellboreis completely perforated and the ability of the fracturing fluidintroduced into the wellbore to enter all intervals is a risk like a“Hail Mary” pass in American Football.

During a refracturing operation with this plugless fracturing invention,operators may introduce the fracturing fluid into all of the existingperforations to sufficiently stress the previously hydraulic fracturedintervals. In another embodiment, they may perforate an unperforatedzone and then begin the process. Once a sufficient volume of fracturingfluid has been pumped, the next interval in between existingperforations would be perforated and fractured sequentially from toe toheel or in a reverse order as discussed above, or in any order deemedsuitable to result in hydrocarbon recovery from the formation. In thecase where other methods such as ball activated sliding sleeves or otherstage tools are present within the wellbore, perforations may beintroduced at any point in between said stage tools.

Other and further objects, features and advantages of the presentinvention will be readily apparent to those skilled in the art upon areading of the description of preferred embodiments which follows whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic illustration of an interval in a wellbore havingthree stages not separated by plugs or isolation means according to thepresent invention.

FIG. 2 is a schematic illustration of the prior art having threefracturing stages separated by plugs.

FIG. 3 is a schematic illustration of the prior art depicting removal ofplugs prior to the recovery stage.

FIG. 4 is a schematic illustration of an example between the prior artmethod and the method of the present invention.

FIGS. 5A-F are schematic illustrations of the steps of creating aninterval with three stages not separated by a plug according to thepresent invention.

FIG. 6 is a schematic illustration of two segments of a well, separatedby a plug according to the present invention.

FIG. 7 is a schematic illustration of the prior art method in anuncemented wellbore.

FIG. 8 is a schematic illustration of the fracturing process in anuncemented wellbore according to the present invention.

FIGS. 9A-B provide an illustration of the microseismic data of wellc-E1-J/94-0-8.

FIGS. 10A-B-C provide an illustration of the microseismic data of wellc-C1-J/94-0-8.

FIG. 11 depicts the data of stages 11, 12 and 13 that were RA traced totrack the distribution of the fracturing fluid introduced using thepresent invention.

FIG. 12 depicts a production log from a completion test on well c-E1-J

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 is a schematic illustration of a multiple stage fracturingprocess according to the present invention. As can be seen, the wellbore20 has a horizontal section 24 extending from a vertical section 22. Thewellbore 20 is equipped with a “Christmas tree” segment 21 of thewellbore above the ground 10. Underground below the shale rock 11 thereis a hydrocarbon containing reservoir 112 which is of interest inhydrocarbon recovery. The horizontal section 24 extends between the heel23 and the toe 27 of the wellbore 20. The horizontal section 24 has acasing 25 that is cemented 26. Two complete stages, stage 201 and stage202 of the fracturing operation are depicted. Stage 201 has an accesspoint 39 made up of perforations 30 and 31 to allow fracturing of thehydrocarbon reservoir 112 with a fracturing fluid 34 resulting infractures 32 and 33. Stage 202 has an access point 49 with perforations40 and 41 and fractures 42 and 43. Perforations 30, 31, 40, 41 50 and 51in FIG. 1 are created by means known to the person skilled in the artsuch as a perforation gun. Stage 203 depicts the process of introducingthe fracturing fluid 34 through access point 59 via perforations 50 and51 creating a stimulating pressure resulting in the fracture thereservoir 112. FIG. 1 illustrates an interval having three stages201,202 and 203 not separated by any diverting means. In this instance,stages 201 and 202 are separated by a predetermined length 29.

FIG. 2 is a schematic illustration of the prior art traditional “Plugand Perf” method. There are two fractured stages, 101 and 102, with athird stage 103, perforated and undergoing fracturing. According to thismethod the reservoir 112 has a horizontal well 124 comprising a casing125 and cemented casing 126. In the first stage 101, perforations 130and 131 are created, followed by introduction of a fracturing fluid 134to create fractures 132 and 133. After completion of stage 101 this“Plug and Perf” method requires the positioning of a first plug 28.After positioning of the plug 28, stage 102 is perforated to createperforations 130 and 131 followed by the introduction of a fracturingfluid to create fractures 132 and 133. After completion of fracturing ofstage 102, a second plug 28 is positioned after stage 102. This “Plugand Perf” process continues until the full length of the horizontalwellbore is fractured and the reservoir 112 is stimulated forhydrocarbon production.

FIG. 3 illustrates FIG. 2 after the “Plug and Perf” process has beencompleted and shows a fully stimulated well 124. The well has a casing125 which is cemented 126. Well 124 consists of several stages 101-105,with each stage being separated by plugs 28. Consequently, in order torecover the hydrocarbons from the reservoir 112, plugs 28 have to bedrilled out by the means of drilling apparatus 70. This “Plug and Perf”prior art process involves several steps adding time and cost to theprocess. For example, the coil tubing or other mechanical drill outdevice is required to remove the plugs (5 plugs here) as discussedabove.

FIG. 4 illustrates an experiment comparing the traditional fracturingprocess with the present invention.

FIGS. 5A-D illustrates the current invention of forming multiple stagesand fracturing each stage without the need of isolation means. Thewellbore 22 has a horizontal segment 24 and a Christmas tree segment 21.FIG. 5A illustrates an introduction of an access point 39 into thewellbore 24 through the casing 25, proximate the toe 27 and distant theheel 23, providing access to the hydrocarbon reservoir 20. In thisexample the access 39 consists of perforations 30 and 31. FIG. 5Billustrates the fracturing of the hydrocarbon reservoir 20 by afracturing fluid 34 through the first access 39. The introduction of thefracturing fluid 34 through the first access point 39 creates fractures32 and 33, resulting in a first stage. FIG. 5C illustrates the start ofa second stage, consecutive to said first stage and not separated fromthe first stage by a plug. A second access 49 is created withperforations 40 and 41 followed by the introduction of the fracturingfluid 34 proximate the second access point to create fractures 42 and 43(see FIG. 5D). FIGS. 5E and 5F illustrate a third stage consecutive tosaid previous stages and not separated from the previous stages by plugsor diverters. This third stage consists of the creation of a thirdaccess point 59 created with perforations 50 and 51 and then fracturingto form fractures 52 and 53. This process may continue by introducingfurther stages, wherein the stages are not separated by any plugs.

FIG. 6 illustrates a first interval 271 comprising a set of severalconsecutive stages 201, 202, 203, and 300 separated from the secondinterval 272 by plug 28. The second interval 272 comprises threeconsecutive stages 201′, 202′ and 203′ once again not separated by anyplugs. The casing 225 of the wellbore is cemented 226.

Each wellbore 224 may comprise a plurality of intervals separated byplugs while each interval may comprise a plurality of stages notseparated by plugs. The number of stages in each interval may vary basedon the geological limitations of the hydrocarbon reservoir, operationalconditions of the well, operational decision of the operator or otherconditions known to persons skilled in the art.

FIG. 7 illustrates another embodiment of the prior art where thewellbore 324 is uncemented. The uncemented wellbore 324 has externalcasing packers 327 to separate the stages 301 from each other. This“plug and perf” method in the uncemented wellbore 324 also requirespositioning of plugs 328 after each perforation 330 has been fractured332. Bridge Plugs 328 are used to direct fluid 334 between fracturedstages inside the casing 325. Bridge Plugs 328 must be removed beforerecovery of hydrocarbons unless Frac Plugs are employed. However,operators often drill out Frac Plugs to improve flow characteristics.

FIG. 8 illustrates the novel process wherein the number of bridge plugs328 are significantly reduced compared to current fracturing techniquesas depicted in FIG. 7. In the present invention, a bridge plug 328 isintroduced after 5 fractured stages. Each of stages 301, 302, 303, 304and 305 comprises a perforation step 330, 340, 350 and fracturing step332, 342, 352 respectively by the fracturing fluid 334. Bridge Plug 328may be required after pumping several fractured stages in order toincrease the flow into new perforations once losses to previousfractures become unacceptable. Alternatively, the effectiveness andefficiency of the fracturing step can be monitored from recording ofmicro seismic events. The monitoring of micro seismic events in the wellcan take place from a proximate offset well or by other means known inthe art.

The novel method as illustrated in FIG. 8 reduces the number of bridgeplugs in the wellbore and therefore effectively reduces the down timeand the costs associated with positioning and removal of plugs.

Example

In the following example, traditional “Plug and Perf” was performed,followed by the method of the present invention, in a horizontalwellbore with a casing, to assess the viability thereof. Referring nowto FIG. 4, the following was conducted:

Stages 101, 102, 103 up to 300 were created using the prior arttechnology “Plug and Perf” and then fractured with use of a plug 28between each of the stages.

Upon completion of fracturing stage 300, a plug 28 was introduced intothe wellbore 124. Wellbore 124 has a casing 125 which is cemented 126.Stage 201 was perforated 230 and 231 and fractured 232 and 233, followedby the perforation 241, 240, 251, 250 and fracturing 242, 243, 252, 253of stages 202 and 203. R/A tracer was pumped (not shown) in stages 202and 203 during fracturing. Three tracers were used: 1 Isotopes in teststage 202 and 2 Isotopes in test stage 203. A finding of 2 Isotopes ofR/A material in these stages, indicated perforations in all stages andconfirmed fracturing coverage using the present invention which resultedin stimulation of all intervals 201, 202 and 203.

This operation was performed on a non-continuous basis in two examplewells. In these example wells, the pumping schedule was such that threezones of interest were perforated without any plugs between them.Radioactive isotopes and micro seismic hydraulic fracture mappingconfirmed the success of the process of the present invention.

Referring now to FIGS. 9A, 9B & 10A, 10B, 10C—two wells (c-C14/94-O-8and c-E1-J/94-O-8) were selected for testing of the present invention.Stages 11, 12 and 13 in well C1 and stages 12, 13, 14 in well E1 wereselected. Micro seismic and radioactive material, were employed todetermine the effectiveness of each “plugless” stage. All test stageswere pumped as planned with some injection rate and pressure differencesobserved in stages 12 and 13 indicating some fracturing fluid wasentering open perforations from previous stages.

Microseismic events suggest new stimulated reservoir volume was createdin the area around new perforations in the direction of maximumhorizontal stress as predicted. Also radioactive isotopes were measuredin the area around the entire test perforations with the highestconcentration of material linking stage fluid pumped to the “Plugless”test stage.

First Well:

See FIGS. 9A and 9B

Plugless Fracturing Experiments, Well c-E1-J/94-O-8, Muskwa Stages 12,13 and 14 Microseismic Events Recorded c-E1-J/94-O-8 Otter Park A wellwith following technical specifications:

-   -   No plug set between stages    -   5 perf clusters/stage    -   125 m stage interval    -   150 T sand, 3375 m3 per stage    -   Field processed data    -   Micro-seismic events, colored dots, are recorded opposite new        perfs and very few events opposite previous stage intervals. As        best illustrated in FIG. 9B the majority of the events of stage        13 are positioned away from the majority of the events the        stage 12. In the same manner the majority of the events of stage        14 are positioned away from the majority of the events of stage        13.

FIG. 12 indicates the productivity from stages 12, 13 and 14 of wellc-E1-J. These stages were not separated by any diverting means. Theproductivity of the three plugless stages is greater than the averageproductivity of the entire wellbore.

Second Well:

See FIGS. 10A, 108, 10C and 11

Plugless Fracturing Experiments, Well c-C1-J/94-O-8, Muskwa Stages 11,12 and 13 Microseismic Events Recorded technical specifications:

-   -   No plug set between stages    -   5 perf clusters/stage    -   125 m stage interval    -   250 T sand, 3375 m3 per stage    -   Field processed data    -   Micro-seismic events recorded opposite new perfs intervals and        very few events opposite previous stage intervals as best        illustrated in FIG. 10C with respect to stages 13 and 12.

As can be seen in FIG. 11, stages 11, 12 and 13 that were Radio Activetraced exhibited favourable overall distribution of the fracturing fluidintroduced in the stages.

If it is determined by observing pressure and rate responses that themajority of fluid is entering the newly perforated interval during thescheduled pumping operations, then that stage will end on scheduleterminating with the firing of the perf guns opposite the next zone ofinterest, while pumping continues.

However, if it is determined that an insufficient percentage of fluidpumped is entering the new perforations, and it is desired to continuepumping, particulate diverting material may be introduced into thefracturing treatment prior to firing the perforation guns across thenext zone of interest. This diverting material, while not a perforationball sealer or other mechanical tool that seals off the flow to thezones below, will permit continuous pumping operations to proceed. Whenthese particulate materials reach all perforated intervals, fluidinjection into these previous perforated intervals will be sufficientlyreduced for the fracturing operation to continue on to the nextperforated interval once the material is displaced past the next zone ofinterest. Once the particulates have cleared the perforation toolopposite the next zone of interest, the guns are fired, creating newperforations and the plugless process continues without pumpingcessation.

As many changes therefore may be made to the preferred embodiment of theinvention without departing from the scope thereof. It is consideredthat all matter contained herein be considered illustrative of theinvention and not in a limiting sense.

1. A method of stimulating an interval in a hydrocarbon reservoirequipped with a deviated wellbore having a casing, wherein said intervalcomprises at least two sequential stages in said wellbore withoutisolation means, said method comprising: i) introducing a first stageby: a) creating at least one access point through said wellbore casinginto a hydrocarbon reservoir; b) introducing at least one fracturingfluid to said aforementioned access point to stimulate hydrocarbonproduction from said hydrocarbon reservoir; ii) introducing a secondstage in the same wellbore by: a) creating a second access point throughsaid wellbore casing, proximate said first stage, into a hydrocarbonreservoir; b) introducing at least one fracturing fluid to said secondaccess point to stimulate hydrocarbon production from said hydrocarbonreservoir; wherein said first stage, and second stage are not separatedby any isolation means; and optionally iii) recovering hydrocarbon fromsaid hydrocarbon reservoir to a surface.
 2. The method of claim 1wherein the access point through the wellbore casing comprises at leastone perforation.
 3. The method of claim 2 wherein said at least oneperforation is substantially perpendicular to the wellbore casing. 4.The method of claim 3 wherein said access point comprises severalperforations.
 5. The method of claim 3 or 4 wherein the perforations arepositioned on the wellbore casing selected from: substantially one linealong said wellbore casing, or substantially around said wellborecasing.
 6. The method of claim 1 wherein the at least one fracturingfluid is selected from the group consisting of liquids, gases and acombination thereof.
 7. The method of claim 6 wherein said fracturingfluid further comprises at least one solid.
 8. The method of claim 1wherein the recovery of hydrocarbon further comprises the steps of:ceasing the introduction of the at least one fracturing fluid; reductionof pressure at the wellbore and recovering the hydrocarbon through thewellbore to the surface.
 9. The method of claim 1 wherein the newinterval comprises at least three stages not separated by any isolationmeans.
 10. A method of stimulating a hydrocarbon reservoir bystimulating at least two intervals according to the method of claim 9,wherein said at least two intervals are separated by isolation means.11. A method of stimulating a new interval in a hydrocarbon reservoirequipped with a deviated wellbore and casing by introducing at least twosequential stages into said wellbore without requiring any isolationmeans, said method comprising: i) introducing a first stage having apredetermined length by: a) creating at least one access point throughsaid wellbore casing into a hydrocarbon reservoir; b) introducing atleast one fracturing fluid to said at least one access point tostimulate hydrocarbon production from said hydrocarbon reservoir; c)monitoring the fracturing pressure in the wellbore; ii) introducing asecond stage having a predetermined length in the same well by: a)creating a second access point through said wellbore casing into ahydrocarbon reservoir proximate the first stage; b) introducing at leastone fracturing fluid to said second access point to stimulatehydrocarbon production from said hydrocarbon reservoir; wherein saidfirst stage, and second stage are not separated by any isolation means;iii) recovering hydrocarbon from said hydrocarbon reservoir.
 12. Themethod of claim 11 wherein each access point comprises at least oneperforation.
 13. The method of claim 12 wherein each access pointcomprises a plurality of perforations proximate each other.
 14. Themethod of claim 13 wherein each perforation is at a distance of lessthan one meter from each other in the same stage.
 15. A method offracturing multiple stages in hydrocarbon deposits for horizontalwellbore intervals without using isolation means, said method comprisingthe steps of: a) selecting a wellbore appropriate for carrying out themethod of fracturing without the use of isolation means; b) selecting anappropriate stage location in said wellbore; c) perforating at least oneperforation, preferably a set of perforations at a first opening for thefirst stage of the wellbore; d) pumping at least one stimulation fluidor sequence of stimulation fluids into said at least one perforation; e)observing the injection rates, and pressure in the stage selected; f)selecting an appropriate stage location in said wellbore; g) perforatingat least one perforation, preferably a set of perforations at aconsecutive opening for the consecutive stage of the wellbore withoutuse of isolation means; h) pumping at least one stimulation fluid orsequence of stimulation fluids into said at least one perforation; i)observing the injection rates, and pressure in the stages; j) optionallyrepeating steps (f) to (i) without isolation means between the stages.16. The method of claim 15 wherein the at least one stimulation fluidfurther comprises radioactive material to determine effectiveness offracturing steps in said perforations.
 17. A process of hydraulicfracturing multiple hydrocarbon deposits in horizontal wellboreintervals comprising fracturing of at least two stages according toclaim
 15. 18. A method of hydraulic fracturing a horizontal wellbore asper claim 15 wherein at least two stages of the well subsequent to thefirst stage are fractured without using conventional divertingtechniques and the location of the subsequent stages are selected byobserving the injection rates, fluid path and pressure differences inthe stage selected by optionally charting micro-seismic and radioactiveindications in said deposit.
 19. A method of stimulating a new interval,in a substantially horizontal wellbore, in a hydrocarbon reservoir, saidmethod comprises introducing two or more sequential stages into saidwellbore without isolation means between said stages, said methodcomprising: i) introducing a first stage by: a) creating a first accesspoint through a wellbore casing into a hydrocarbon formation; b)introducing at least one fracturing fluid to said first access point ata sufficient rate, to stimulate hydrocarbon production from saidhydrocarbon formation; c) monitoring operating conditions of saidwellbore at a predetermined time throughout said method; ii) introducinga second stage in the same wellbore by: a) creating a second accesspoint, proximate said first stage, through a wellbore casing into ahydrocarbon formation; b) introducing at least one fracturing fluid tosaid second access point at a sufficient rate, to stimulate hydrocarbonproduction from said hydrocarbon formation; c) monitoring operatingconditions of said wellbore at a predetermined time throughout saidmethod; iii) introducing a consecutive stage (or stages) in the samewellbore by: a) creating at least one consecutive access point through awellbore casing into a hydrocarbon formation proximate a previous stage;b) introducing at least one fracturing fluid to said consecutive accesspoint at a sufficient rate, to stimulate hydrocarbon production fromsaid hydrocarbon formation; c) monitoring operating conditions of thewellbore at a predetermined time throughout said method; d) terminatingstimulation to allow for recovery of hydrocarbons; and e) recoveringhydrocarbons from said hydrocarbon reservoir; wherein said two or moresequential stages are not separated by any isolation means.
 20. Aninterval in a hydrocarbon reservoir equipped with a deviated wellbore,said interval comprising at least two sequential stages not isolated byany isolation means.